The first scanner you add on each side, more than doubles the ships detection range, so it represents good value.

Beyond 4 or 5, each successive scanner added provides very little gain, which is probably why none of the built-in designs have more than 5 on a side.

The actual detection range is also affected by the number of stealth units the enemy ship has.
It is worth noting that 46% of ship types have no stealth units, and 85% have 4 or less (the average is 2.3).

Engines mounted on the rear and sides, increase thrust (acceleration & deceleration) and turning respectively.
The actual increase in thrust/turning per engine, depends on the total weight of the ship.
Top speed is fixed for all ships regardless of thrust.

For any given weight, the relationship between the number of engines and the thrust/turning, is linear - ie. Double the number of engines does mean double the thrust/turning.

However, as the total weight of the ship increases, the effect of adding more engines is lessened.

It is important to note that engines are by far the heaviest ship components, with a weight of 16, compared to just 2 for the next heaviest, the repair bot (excluding Cargo & Passengers). This means it is difficult to create a ship which has both high thrust and turning.

AI pilots do not make good use of ships with high thrust, and are generally better off flying ships with high turning instead. The downside to this, is that they are prone to bumping into asteroids and other ships, leaving them stationary and vulnerable.

The choice of ship for you to use yourself, is a matter of personal preference. Ships which turn quickly are easier to use for novice pilots, whilst high-thrust ships are better suited to slashing attacks.

Note that 73% of ships have a Turning rating between 60 and 75.
As a result, 60-65 could be considered a minimum required turning ability.
Anything over 75 can be considered outstanding, and will have a definite edge over the vast majority of other ships.

Thrust ratings are far more evenly spread, and there is no real minimum required to be competitive.

Shields, Command Centres & Repair Bots

Shields absorb damage, protecting the components behind them.

They are directional - ie. If a ship is hit from the front, only the front shields will be damaged. However, if a missile hits an unshielded side, the damage will be spread between all interior components at random.

Regular (blue) shields absorb 4 times the damage of other components, and super-shields (yellow) 8 times.

There is not way to predict the actual number of components which will be damaged by a hit, as it is largely random, although missiles with larger warheads do generally cause more damage.

It is important to note that both types of shield cost 4 times as much when placed at the rear of a ship.

Command Centres are the most important components - if they are all destroyed, then so is the ship.
Having spare command centres increases the durability of a ship significantly.

Each repair bot (up to a maximum of 4) has a 10% chance of repairing a random damaged component, each turn.

Combining large numbers of command centres with repair bots, can make a ship virtually indestructible.
Whilst this can be an alternative to shields, it's worth remembering that shields absorb 4 times the damage that command centres do, and also, that an unshielded ship risks being crippled by hits to its engines and missile launchers.

Missile Launchers

Missile Launchers are the most expensive ship components, and it is generally not worth having the maximum number (4) except on ships with a very high overall cost.

2 launchers is usually the bare minimum, but since 2 missiles are not enough to destroy most installations (except from the rear), 3 is preferable.

It's rarely a good idea to fire 4 missiles in one turn (it's unlikely they'll all hit, meaning you'll get a poor accuracy score), but having 4 launchers does allow you to fire twice every turn.

Missiles

It is important to note that although each set of 5 missiles costs just 5 points, there is an additional charge of 4 points for each different type of missile carried (not including the first one).
All my ships use a combination of Plectrons and Daycorns, or Yataris and Daycorns if they are to be AI controlled.

Plectron (purple)
The most useful missiles due to their large warhead and lack of guidance, which is a huge asset once you get used to aiming them. Not much use to AI pilots though, who can't seem to aim, and will probably hit you more often than the enemy.

Daycorn (yellow)
By far the best dogfighting missile, due to their outstanding agility. They do only have about 2 turns worth of fuel though.

Yatari (cyan)
The best missile for inexperienced and AI pilots to use against installations such as Turrets, Factories, etc. Don't even try and use them in a dogfight though. Interestingly, their thrust is so low that they will be almost stationary if launched while flying backwards at speed. Experienced pilots are much better off with Plectrons.

Geenee (blue)
These are supposed to be a compromise between agility and power. In practice, their turning is not good enough for them to be useful in a dogfight against most enemies. They're best used in extremely cheap wingman ships, where it would be too expensive to carry more than one type of missile.

Drachan (white)
These do not track friendly ships or asteroids, although they don't actively avoid them either as the game suggests. Perhaps useful if you're sick of being shot at by your wingmen, but you're better off with Daycorns really.

Orik (orange)
These are useful as they are fairly hard to shake off, and will continue to track their target for a long time. However, I'd still take Daycorns over them.

A kill rate of 2-2.5 per mission is pretty normal for me.
It's probably because my custom wingman designs are so amazingly awesome that they steal all my kills

Actually, it's probably a combination of a few factors:
* my own custom ship has a turning rating of 44 (but at least I never eject or hyperspace),
* I don't bother with civilian ships (leave them to my wingmen),
* I'm just not very good?

In fairness, I do usually manage a higher mission success rate though -
note: I only reinstalled quite recently.
(I'm not sure what was special about the highest score - why there's an "s" on the end of my name, why the success rate's so low, or why it got so many gold crosses??)

There is a thread called 'Critical Mass Ship Editor Utility' which is currently the 6th item down on the board. Take a look at the instructions I posted on how to change the ship Designs file. Try using the modified file for a bit and see how it affects your results. Be forewarned, you will have a VERY difficult time getting past mission 70.

On the second page of the ship editor thread is a post that is second from the top. It gives detailed instructions for changing the designs.dat file to a modified version that allows you to get 5 of your custom designs into the playlist for the enemy to use. Among other things, that modified file contains a few of my own custom designs. They are intended to make you work your rear end off trying to stay alive. Try it. You'll either love it or hate it because you get clobbered so often.

You can switch back and forth between the modified and original designs file so long as you are not flying a ship that is unique to one or the other.